The provision requires state, county and local governments with a history of discrimination to obtain advance approval from the Justice Department, or from a federal court in Washington, for any changes to election procedures. It now applies to all or parts of 16 states.

In a 2-1 decision, the U.S. Court of Appeals for the District of Columbia Circuit said that Congress developed extensive evidence of continuing racial discrimination just six years ago and reached a reasonable conclusion when it reauthorized section 5 of the law at that time.

The appellate ruling could clear the way for the case to be appealed to the Supreme Court where Chief Justice John Roberts suggested in a 2009 opinion that the court’s conservative majority might be receptive to a challenge to section 5.

Judge David Tatel wrote for the Court of Appeals majority that the court owes deference to Congress’ judgment on the matter.

“Congress documented hundreds of instances in which the attorney general, acting pursuant to section 5, objected to proposed voting changes that he found would have a discriminatory purpose or effect,” Tatel wrote.

Tatel said that in reauthorizing the law in 2006, Congress found serious and widespread intentional discrimination. The attorney general blocked discriminatory voting changes on 626 occasions, while state and local units of government withdrew over 800 proposed voting changes in response to Justice Department inquiries, Tatel said in summarizing the evidence Congress compiled.

In dissent, Judge Stephen Williams said the Voting Rights Act “imposes rather extraordinary burdens” based on information about discrimination that is several decades old.

Williams said the law applies substantive standards “quite different from those governing the rest of the nation.”

Jurisdictions covered by Section 5 of the law were chosen based on whether they had a test restricting the opportunity to register or vote and whether they had a voter registration or turnout rate below 50 percent.

But the law specifies that the elections for which these two criteria are measured must be ones that took place several decades ago, said Williams.

“It goes without saying that racism persists,” wrote Williams. “But without more evidence distinguishing current conditions in the covered jurisdictions from those in the uncovered ones,” the law’s “coverage formula appears to be as obsolete in practice as one would expect” for evidence that is several decades old.

Addressing Williams’s point, Tatel said the question is not whether old data is being used, but whether it helps identify the jurisdictions with the worst discrimination problems.

“If it does, then even though the formula rests on decades-old factors, the statute is rational,” said Tatel.

Tatel said Congress dealt with the issue of old information by adding a “bailout” provision to the law allowing jurisdictions with clean discrimination records to seek an end to their preclearance obligations under Section 5.

Section 5 currently applies to the states of Alabama, Alaska, Arizona, Georgia, Louisiana, Mississippi, South Carolina, Texas and Virginia. It also covers certain counties in California, Florida, New York, North Carolina and South Dakota, as well as some local jurisdictions in Michigan and New Hampshire.

Tatel, an appointee of President Bill Clinton, was joined in his ruling by Judge Thomas Griffith, an appointee of President George W. Bush. Williams is an appointee of President Ronald Reagan.

The 2-1 decision came in a constitutional challenge by Shelby County, Ala., to federal election monitoring, which is designed to prevent racial discrimination. The appeals court was upholding a ruling eight months ago by U.S. District Judge John Bates.

The Voting Rights Act “is a cornerstone of civil rights law, and the department will continue to vigorously defend it against constitutional challenges,” said Justice Department spokeswoman Xochitl Hinojosa.

Friday’s ruling “is the latest in an unbroken line of cases upholding the constitutionality of the Voting Rights Act’s most effective protection,” said Debo P. Adegbile, interim president and director-counsel of the NAACP’s Legal Defense and Educational Fund. The fund intervened in the case to defend Section 5 on behalf of several African American community leaders and voters in Shelby County.

Opponents of the Voting Right Act saw Chief Justice Roberts’ 2009 Supreme Court decision as an invitation to challenge the constitutionality of Section 5.

“Things have changed in the South,” the chief justice wrote in 2009. “Voter turnout and registration rates now approach parity. Blatantly discriminatory evasions of federal decrees are rare. And minority candidates hold office at unprecedented levels.” Roberts said the Voting Rights Act “imposes current burdens and must be justified by current needs.”